R ecognize these rows and columns? You may remember a detail or two about this mighty table’s organization from a long-ago chemistry class. Elements are ordered according to their number of protons, or atomic number. Metals are mostly to the left and nonmetals to the right.
When Dmitrii Mendeleev proposed his periodic table 150 years ago, no one knew what was inside an atom. Today, we know that an element’s place on the table, along with its chemical properties, has a lot to do with the element’s proton number as well as how its electrons are configured.
In one glance, you can see the elements that make up nature’s entirerepertoire of chemical substances plus how those elements relate to one another. But the elements are also individuals, with scientific idiosyncrasies and nuanced stories of discovery.